Nothing fancy here other than a rectangular dump chute....which is something we don't see much in the USA but is somewhat popular with folks in foreign lands. A number of years ago we collaborated with some folks in Chile about dump chute/valve design and their rectangular dump chute seamed to work just fine. The cross-sectional area of the valve was the same or greater than the A H Stock 10" (square) Newtown dump.

Fast forward to today and we certainly see the a version of the rectangular chute in the Newton swivel chute. At the end of the day on a gravity dump tank, it really is about the size of the opening and the use of the available head pressure.

Also of note on the Green Pond tanker, the use of check valves on the direct fill lines and the use of cam lock hose connections on the pre-connected fill hoses.